Customer loyalty is a key d river o f financial p erformance f or o nline firms. The e ffect o f service q uality o n customer loyalty h as b een well es tablished. Y et, there is a p aucity o f r esearch that has s tudied the c ost o f obtaining s ervice quality d uring t he s ervice process a nd t he s ervice outcome i nfluenced by s uch cost. We extend p revious re search a nd p ropose t he 3S Customer Loyalty M odel b y integrating s acrifice and s ervice outcome a s a dditional i mportant service d imensions t ogether with service q uality when p redicting o nline customer loyalty, and examining how their influences on loyalty vary across customers with different degrees of product k nowledge. Further, we t heorize t hat service quality a nd sacrifice -- as service p rocess d imensions -- influence s ervice o utcome, and w e theorize h ow “ live help” technology improves customer p erceptions o f service q uality and s acrifice. T he e mpirical r esults indicate that 1 ) c ustomer loyalty i ncreases w ith h igher perceived service quality, lower perceived sacrifice, and better perceived service outcome, 2) service quality and s acrifice i nfluence s ervice o utcome, 3 ) c ustomer p roduct k nowledge n egatively moderates the relationship b etween s ervice q uality a nd o nline c ustomer l oyalty and p ositively moderates t he relationship between s acrifice a nd customer loyalty, and 4 ) live h elp technology en hances service q uality a nd r educes sacrifice. These findings support the theoretical importance of including sacrifice and service outcome (parallel with s ervice quality) as a ntecedents of online customer loyalty. O ur s tudy a lso a dvances t he t heoretical understanding o f what service p rocess c onsists of and how t he s ervice p rocess (i.e. s ervice q uality and sacrifice) influences service outcome.